Biodiesel is a fuel derived from vegetable oils or animal fats. In use, it has similar properties as conventional (petroleum-based) diesel fuel. A common form of biodiesel includes the methyl ester or ethyl ester of fatty acids obtained from vegetable oil or animal fat. Vegetable oils and animal fats are generally triglycerides. Biodiesel is usually produced either by the direct esterification of fatty acids or by the transesterification of the source oil.
Glycerol is a byproduct of the production of fatty acids and of the transesterification process used to produce biodiesel. Depending on the particular fat or oil used as the biodiesel source, glycerol as a byproduct can comprise up to approximately 9-11 wt. % of the starting material.
Several markets already exist for glycerol as a byproduct of fatty acid or biodiesel production. Glycerol is a common feedstock in the synthesis of various chemicals, and has a number of uses in pharmaceutical formulations. However, these markets typically require highly purified glycerol. Such purification can be costly and must be done in a large-scale operation to be profitable. In addition, as the volume of biodiesel production (and thus byproduct glycerol production) increases, existing markets for glycerol are becoming saturated and the price paid for the glycerol will decrease, adversely impacting the economics of biodiesel production.
In addition, the need to supply raw material monohydric alcohols to a biodiesel production facility, and the simultaneous need to ship out side product glycerol from the facility can increase the cost for the biodiesel produced and can limit the facility siting geographically to those locations with good and inexpensive transport as well as proximity to markets for the glycerol and supplies for the alcohols. Further, because the price paid for the glycerol depends on the use it is put to, acceptable facility siting can be limited even further to those locations readily accessible to facilities that will pay a premium for the glycerol, such as pharmaceutical, cosmetic, and personal care facilities.
In addition, the transport itself of the alcohols and the glycerol is an undesirable aspect of many proposed biodiesel facilities. Such transport increases the consumption of motor fuels which increases air pollution and can lead to other environmental problems. Use of the glycerol on site as a valuable material can reduce these unfortunate problems with conventional biodiesel operations.
Finally, the need to supply monohydric alcohol from outside sources to a biodiesel facility means that other resources will be needed to support the biodiesel production at that facility. If instead, this raw material can be produced on-site from materials that are readily available at the location, fewer outside resources will be needed to support the facility and resulting in a smaller environmental footprint for the facility.